Typically, various kinds of sensors and navigation instruments including a radar, a fishfinder, and a GPS receiver are carried in a ship. In many cases, these devices are interconnected through network(s) including a Local Area Network to establish a network system. JP2009-58246A discloses this kind of network system for the ship instruments.
The ship instrument network system disclosed in JP2009-58246A includes, as its main components, a server device having a server function, two or more sensors for detecting the same physical property, and two or more display units for displaying the data detected by these sensors.
The server device selects one from two or more sensors, and shares the detection value of this selected sensor among the two or more display units. Particularly, the ship instrument network system has two or more communication networks, and the detection value of the sensor can be shared among the two or more communication networks.
In the network system of JP2009-58246A, the sharing of data is performed by instructions only from the server device having the server function. Therefore, when a failure occurs in this server device, this single failure can easily make the sharing of the sensor detection value impossible. Thus, there is a need for an improvement in this regard.
In addition, since, in the network system of JP2009-58246A, the communication network to which the server device is directly connected and the communication network to which the sensors are directly connected are separate networks, the network system may also have the following disadvantage.
The disadvantage is that the detection value of the sensor needs to pass through a network instrument which connects the different communication networks, which creates a time lag in the transmission. Moreover, when a failure occurs in the network instrument, the system cannot use the sensor and the like connected with this network instrument.